Ecological differentiation facilitates fine-scale coexistence of sexual and asexual Boechera

Premise of the study: Ecological differentiation (ED) between sexual and asexual organisms may permit the maintenance of reproductive polymorphism. Several studies of sexual/asexual ED in plants have shown that the geographic ranges of asexuals extend beyond those of sexuals, often in areas of higher latitude or elevation. But very little is known about ED at fine scales, wherein coexistence of sexuals and asexuals may be permitted by differential niche occupation. Methods: We used 149 populations of sexual and apomictic lineages in the genus Boechera (rock cress) collected across a portion of this mustard’s vast range. We characterized reproductive mode, ploidy, and species identity or hybrid parentage of each individual, and then used a multi-pronged statistical approach to 1) identify ED between sexuals and asexuals; 2) investigate the impacts of two confounding factors, polyploidy and hybridization, on ED; and 3) determine the environmental variables underlying ED. Key results: We f...